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Each group of 6 cells is connected to a battery monitoring circuit (shortened as BMC later).

This circuit measures:

  • The voltage of each cell

  • The current delivered by the group

    • This is done by forcing the battery to deliver current through a resistor with a tiny resistance. This resistor, called a shunt/shunt resistor, follows Ohm’s law: V=IR

    • This implies that I=V/R, which means that the current passing through a shunt is equal to its voltage (which can be measured easily), divided by its resistance (which is a known constant).

And it sends:

Note

We are not exactly sure of everything yet.

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Info

The ports we are interested in:

  • PA9: SCL_1, Serial Clock line for I2C 1, to configure BMC 1

  • PA10: SDA_1, Serial Data line for I2C 1, to configure BMC 1

  • PA7: SCL_2, Serial Clock line for I2C 2, to configure BMC 2

  • PB4: SDA_2, Serial Data line for I2C 2, to configure BMC 2

  • PA12: CAN_TX, Transmit line for CAN

  • PA11: CAN_RX, Receive line for CAN

  • PA3: OVERCURRENT, receives 5.5 V when an overcurrent occurs, and 0 V otherwise

Speculated ports:

  • PA5: VCOUT1_FILT, receives 1.47-1.53 V (REF_SEL=0) / 2.94-3.06 V (REF_SEL=1), representing the cell voltages for cells 1-6

  • PB0: ADC1_FILT, receives 0.25-1.25 V (REF_SEL=0) / 0.5-2.5 V (REF_SEL=1), representing the cell current for cells 1-6, as measured by a 1-milliohm shunt

  • PB1: VCOUT2_FILT, receives 1.47-1.53 V (REF_SEL=0) / 2.94-3.06 V (REF_SEL=1), representing the cell voltages for cells 7-12

  • PA2: ADC2_FILT, receives 0.25-1.25 V (REF_SEL=0) / 0.5-2.5 V (REF_SEL=1), representing the cell current for cells 7-12, as measured by a 1-milliohm shunt

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  • What is REF_SEL set to for the battery monitoring boards?

  • Are our speculated ports correct?Why are we reading the battery and voltage information via both I2C and analogue pins?

  • How should the MCU beacon itself to the FC (i.e. so that the FC is aware that the MCU on the power module is there)?

  • What should be sent over CAN?

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